EAST LANSING, Mich. — Downy mildew has been confirmed in cucumber fields in southeastern Michigan.

Michigan State University (MSU) Department of Plant Pathology Professor Mary Hausbeck said that while the disease has been found at three farms in Michigan’s Monroe County area, it is being treated and is under control on those farms.

Downy mildew causes symptoms on leaves similar to mosaic or angular leaf spot. A distinguishing symptom of downy mildew is dark, purplish-gray fuzz on the underside of the leaf that gives it a “dirty” or “velvety” appearance. The fuzz may be most evident in the morning and can infect leaves of all ages.

Hausbeck said the infected fields are being closely monitored, but scientists are concerned about the airborne spread of spores to other areas. With spores being carried by the wind, she said the eastern part of Michigan is “at moderately high risk because of how the air currents have flowed in the last few days.”

“Northwest and West Michigan are in good shape,” she said.

According to Hausbeck, MSU scientists have spore traps in place in six counties to “continue to monitor the spore load.”

Hausbeck said several fields in Ohio are showing downy mildew symptoms, “although the fungicide program is keeping the disease in check.”

However, growers in Ontario, Canada, have not fared so well. According to Hausbeck farmers there are experiencing an outbreak that is not being controlled.

The threat of downy mildew has West Michigan cucumber grower Jeff Crawford concerned.

Crawford, who grows about 500 acres of cucumbers on his 1,400-acre Montcalm County farm, said he lost about 60 percent of his crop last year to downy mildew.

It was the first time Crawford had an outbreak at his operation. “I had my scouts look at it and they misdiagnosed it. They thought it was angular leaf spot,” Crawford said. “Then I finally got the word that it was downy mildew. I had zero experience with it, but I learned a lot about it right away.”

Last year’s experience has Crawford on alert this year.

“We lost critical time last year. We’re watching our crop closely this year,” he said. “We’re watching the winds with this outbreak in Southeast Michigan. We’re scared to death of a southeast wind.”

Walking through a field on Friday that’s about two weeks away from harvest, Crawford said he is already spraying some of his crop with a fungicide as a precautionary measure.

“The best way is to be prepared, to have fungicide out there,” he said.

He said he currently is using a less expensive combination of Bravo and Mancozeb fungicides and estimated the additional expense at about $10 per acre per application. With a 52-day growing cycle he figures he’ll spray at least four times. If he uses only the less expensive fungicides he’ll spend about $20,000 more this year on his crop.

If downy mildew is confirmed in his area and he opts for the more expensive sprays, Crawford said he would expect to spend $16-$20 per acre per application.

Crawford has cucumbers in all stages of production. While he expects to begin harvesting some within the next two weeks, he just finished planting on Friday. He’s concerned about the early detection of downy mildew this year. Last year it didn’t crop up until early August, but this year’s first detection was made in June.

Crawford is optimistic that his heightened awareness of the threat of downy mildew will help him stay on top of a possible outbreak.

“One more year like last year and I’m going to be out of the pickle business,” Crawford said.

Farmers who suspect downy mildew is on their cucumbers, cantaloupes or other vine crops should contact a local Extension office immediately to report it.

This farm news was published in the July 19, 2006 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee.